Capacitorless Solid-state Power Filter for Single-phase DC-AC Converters

Converters rely on passive filtering as a crucial element due to the high-frequency operational characteristics of power electronics. Traditional filtering methods involve a dual inductor-capacitor (LC) cell or an inductor-capacitor-inductor (LCL) T-circuit. However, capacitors are susceptible to wear-out mechanisms and failure modes. Nevertheless, the necessity for monitoring and regular replacement adds to an elevated cost of ownership for such systems. The utilization of an active output power filter can be used to diminish the dimensions of the LC filter and the electrolytic dc-link capacitor, even though the inclusion of capacitors remains an indispensable part of the system. This paper introduces capacitorless solid-state power filter (SSPF) for single-phase dc-ac converters. The proposed configuration is capable of generating a sinusoidal ac voltage without relying on capacitors. The proposed filter, composed of a planar transformer and an H- bridge converter operating at high frequency, injects voltage harmonics to attain a sinusoidal output voltage. The design parameters of the planar transformer are incorporated, and the impact of magnetizing and leakage inductances on the operation of the SSPF is illustrated. Theoretical analysis, supported by simulation and experimental results, are provided for a design example for a single-phase system. The total harmonic distortion observed in the output voltage is well below the IEEE 519 standard. The system operation is experimentally tested under both steady-state and dynamic conditions. A comparison with existing technology is presented, demonstrating that the proposed topology reduces the passive components used for filtering.